Variable resistance



Feb. 21, 1928.

W. L. BURNAM VARIABLE RESISTANCE Filed Jan. 27, 1926 1 m nkvm u o 5 WmP3,, l m

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Patented Feb. 21, 1928.

WILLIAM LEE :Bnnmur, or KANSAS CITY, mssouar.

VARIABLE nnsrsrancn.

Application filed January 27, 1926. Serial No. 84,205.

This invention relates to a liquid rheostat which is adapted for use asstatic eliminator. object of this invention is to provide a. simple andeflicient variable resistance device which is adjustable and adapted tobe connected preferably between the aerial and the antenna post of aradio set, whereby the resistance of the circuit can be varied andstatic and other disturbing frequencies eliminated.

A further object is to provide such a device which is simple to operateand durable andeconomical in construction.

The invention is illustrated in the drawings, of which Figure 1 is aside elevation of the device mounted on the panel board;

Figure 2 is a longitudinal section through the device taken on theline22 of Figural; Fgure 3 is .a longitudinal section taken at rightangles to the section line of Fig- Figure 4 is a horizontal sectiontaken on the line H of Figure 3.

The form of the invention shown in the drawings is a preferred form,although it is understood that modifications in the construction andarrangement of the parts and the character ofthe materials used may beadopted without departing from the spirit of the invention as set forthin the appended claims.

in its general aspect the invention comprises a tubular container inwhich a body of liquid is disposed. Disposed within the container is anadjustable electrode which may. be wholly or partly submerged in theliquid. One end of the container is c0nnected to the antenna circuit,for instance, and

the other end is connected to the radio set.

By adjusting the distance between the bottom of the adjustable electrodeand the bottom of the container the resistance in circuit can be variedand it is found that this arrangement will permit radio signals to passand at the same time will shut out the static and other extraneousnoises. It also seems to decidedly improve the quality of the tonecoming from the set. The adjustable electrode is manipulated by throughthe side of a container and may be mountednnthe side of a panel board.

' In the preferred construction shown in the drawings, the inventioncomprises 2; containany material w ch will hold water and is er 10,preferabliyl iin tubular form, made of a knob which extends not aconductor of electricity. The upper and lower ends of the container areclosed by threaded caps 11 and 12 which are screwed on .the ends of thetube, packing rings 13 and 14 making the joint tight. The caps areprovided with threaded stems 15 and 16 on which thumb nuts 17 and 18 aremounted for the purpose of permitting connection to conducting wires.Within the container or tube is a body of liquid 19 preferably water.Dependent into the liquid is an electrode 20 mounted on a rack bar 21which is slidable in acurved guide plate 22. This guide plate isfastened against the face of an insulating block 23 which is screwed tothe side of the tube 10. An insulating sleeve 24 is threaded into anaperture in the block 23 and an aperture in the side of the tube and inthe panel board 25. Suitable washers 26 and 27 are disposed on each sideof the panel board and threaded on this sleeve 24. Within the sleeve isa shaft 28 on the outer end of which is mounted a knob 29 with a pointer30 traveling over a dial 31. The other end of the shaft .28 is providedwith a pinion 32engaging with the rack bar 21 to move it upwardly anddownwardly. As shown in Figure 2 one side of the guide plate 22 is splitto provide a spring finger 33 which will frictionally bear againsttheraclr bar to maintain it in any position in which it is left. Theguide plate 22 supports a spring arm 34 which extends upwardly therefromand bears as at 35 against the bottom of the cap 11, thus making thecircuit contact with the binding post stem 15, the caps 11 and 12 beingof metal. It will be observed that as the knob 29 is operated to raiseand lower the rack bar the distance between the bottom of the electrode20 and the cap 12 through the liquid 19 can be varied, thus varying theresistance introduced into the circuit by reason of this liquid paththrough which the signal currents have to pass. It is the provision ofthis variable liquid path in the circuit, preferably the antennacircuit, which seems to cause the improvement in the operation of theset and in the elimination of static.

What I claim is:

1. In a variable resistance, a liquid receptacle of insulating materialprovided with metal caps having means for securing circuit wiresthereto, a guide member in the receptac le, a rack mounted in themember, an electrode carried by the rack, a pinion meshing with therack, means for operating the pinreceptacle of insulating materialprovided ion, and a member carried by the guide mem' with removablemetal caps having threaded her and permanently engaging the upper stemson which thumb nuts are mounted, an cap of the rece tacle. insulatingblock secured to the casing, a guide 2. In a varia le resistance, aliquid recepsecured to said block, a rack slidably mounttacle ofinsulating material provided with ed in the guide, an electrode securedto the metal caps having means for securing circuit lower end of therack, a spring carried by wires thereto, a guide member in the receptheguide and engaging the rack, an insutacle,a rack slidably mounted in thememlating sleeve in openings in the insulating her, a spring carried bysaid member and enblock and the receptacle, a shaft mounted in gagingthe rack to hold it in position, an the sleeve and provided with a knobat its electrode carried by the rack, a pinion meshouter end, a pinionon the inner end of the ing with the rack, means for operating the shaftand meshin with the rack, and a pinion, and a member carried by theguide spring arm secure to the guide and permamember and permanentlyengaging the upnently engaging the upper cap of the recepper cap of thereceptacle. tacle.

8 In a variableresistance, a tubular liquid 4 WILLIAM LEE BURNAM.

